Functions of camera accessories have recently become more complicated with an advance in camera function. A microcomputer has heretofore been used in only a camera body, but it is at present used in accessories to execute various camera operations in cooperation with a microcomputer in a camera body. In this case, operations in the accessory are executed in response to control signals transmitted from the microcomputer in the camera body via electric contacts connected with each other on mounting of the accessory (refer to Japanese Laid-Open Patent Application Sho 62-229237). In most cases, power for circuits for the accessory is supplied from the camera body via similar contacts.
A problem resides in the reliability of control and communication signals and power supply lines. These lines connect a camera body and an accessory via electric contacts and are designed to provide a high reliability so that no problem occurs on normal use. However there are fears that the microcomputer in the accessory malfunctions due to supply of insufficient power to the accessory and that a program will run away due to pick-up of noises during communication.
Another problem resides in power consumption. When camera operation is executed, power as much as double of that consumed in a conventional camera is consumed since circuits in both the camera body and camera accessory work simultaneously. Since less operations are executed in the accessory than those in the camera body, the microcomputer in the accessory is on stands by for a longer time from the completion of a given operation to the next operation. During this standby period, the circuits in the accessory continues to consume some electric power, resulting in waste of power.